But the independent board of inquiry also found that Palestinian militant groups hid weapons at three empty U.N. schools in Gaza and that in two cases Palestinian militants "probably" fired from the schools. Ban called that "unacceptable."

The 2014 war was the most devastating for Gaza's 1.8 million people, killing more than 2,200 Palestinians, a majority of them civilians, according to U.N. figures. Seventy-two people were killed on the Israeli side, including 66 soldiers.

In one case, the new inquiry said, a U.N. girls' school was hit by 88 mortar rounds fired by the Israeli Defense Forces. In another case, another girls' school was hit by direct fire from the IDF with an anti-tank projectile. A third girls' school was hit by an IDF missile.

At a fourth girls' school, the inquiry said, "no prior warning had been given by the government of Israel of the firing of 155 MM high explosive projectiles on, or in the surrounding area of the school." At a co-ed college, one block was damaged by a projectile fired by an Israeli tank.

The inquiry also found weak security at the U.N. schools where weapons were found. It said in two cases that a "Palestinian armed group" likely fired from two of the schools.

The U.N. released its summary of the report but said the full 207-page report is private. The inquiry looked at 10 incidents. Ban's statement stressed that the board of inquiry "does not make legal findings" and was not tasked with addressing the wider issues of the Gaza war.

In a statement, Israeli Foreign Ministry spokesman Emmanuel Nahshon said, "All of the incidents attributed by the report to Israel have already been subject to thorough examinations, and criminal investigations have been launched where relevant. ... Israel makes every effort to avoid harm to sensitive sites."

Nahshon's statement added, "The executive summary of the report clearly documents the exploitation by terrorist organizations of U.N. facilities in the Gaza Strip."

There was no immediate comment from the Palestinian mission to the U.N.

The current president of the U.N. Security Council, Jordanian Ambassador Dina Kawar, told reporters she couldn't comment because she hadn't read it yet.

Ban ordered the inquiry in November after thousands of buildings were destroyed and at least 223 Gaza schools, either run by the U.N. refugee agency or the Islamic militant group Hamas government, were hit in the fighting. Weapons caches were found in several U.N. schools that weren't being used at the time.

When Ban visited Gaza in October, he said the destruction was "beyond description" and "much more serious" than what he witnessed in the Palestinian territory in 2009 in the aftermath of a previous Israel-Hamas war.

Ban said Monday he has established a group of senior managers to look into the inquiry's recommendations, which include asking Israel to commit to warning the U.N. "in the event that it plans any future military operation in proximity to United Nations premises."

The inquiry's summary suggests a hotline be established between the Israeli military and the U.N. agency for Palestinian issues for "emergency coordination."